A knee brace can be worn by a post-operative patient who has had knee surgery. Knee braces are also worn by persons who suffer knee instabilities or other persons engaged in sporting activities to prevent sporting injuries to the knee. The common purpose of the knee brace is to provide exterior support for the knee to prevent any unnatural movements of the knee joint which could injure or reinjure the knee ligaments, while allowing the normal swinging movement of the knee joint about a horizontal axis through the knee (viz., forward and backward movement of the lower leg or tibia relative to the upper leg or femur, as in a normal walking motion). One type of motion to be prevented by a knee brace is a sudden movement of the upper and lower legs to one side or the other. Another type of motion to be restrained is a twisting or rotation of the lower leg relative to the upper leg about a vertical axis.
Several such knee braces have been developed in recent years. These prior art knee braces include the braces disclosed in U.S. Pat. No. 3,669,105 to Castiglia and U.S. Pat. No. 4,372,298 to Lerman. The Castiglia brace has a pair of lateral uprights extending along the outside of the leg and articulated at the outside of the knee joint by a single axis pivot pin. Upper and lower contact pads attached to the ends of the uprights contact the outside of the thigh and lower leg above and below the knee joint. Curved rigid bars extend from the upper and lower contact pads around and in front of the upper and lower leg to the inside of the knee joint where the ends of the curved bars are interconnected by another single axis pivot pin. A condyle pad attached to the inside pivot pin engages the inside of the patient's knee joint. The pad rotates about the pivot pin axis independently of the upper and lower curved bars. A pair of wide elastic rubber straps attached to the upper and lower contact pads encircle the leg above and below the knee joint to support the curved bars on the upper leg and lower leg. A smaller elastic strap is attached to the lower contact pad and is spiralled upwardly around the back of the knee and attaches to the upper contact pad. This elastic strap provides a de-rotation capability for preventing the lower leg from rotating or twisting relative to the upper leg about a vertical axis.
The knee brace disclosed in the patent to Lerman has upper and lower U-shaped supports for the upper leg and the lower leg and two pairs of upper and lower support arms extending along the lateral and medial sides of the patient's leg between the upper and lower supports. The support arms pivot about a polycentric pivot joint adjacent the lateral and medial sides of the knee joint. Upper and lower flexible elastic straps secured to the upper and lower supports extend around the upper and lower leg for attaching the knee brace to the leg. Condyle pads inside the polycentric pivots apply pressure to the lateral and medial sides of the knee joint. Upper and lower elastic straps adjacent the condyle pads wrap around the knee joint for holding the condyle pads in contact with the lateral and medial sides of the patient's knee joint.
The Lerman knee brace is an improvement over the Castiglia brace in the sense that the Lerman brace is more comfortable, in part, because it eliminates pressure points at the front of the legs. The Lerman brace also provides better overall contact with both sides of the knee joint, by providing the lateral and medial condyle pads which are held in pressure contact with the knee joint through the full range of motion at the knee. However, both of these knee braces must be held in the proper fixed position around the patient's knee in order to provide the required support throughout the full range of motion at the knee. Thus, there is a need to provide a knee brace which can maintain the required support through constant use of the brace. Some braces currently used today have a tendency to twist about the leg or slip down along the leg while the brace is worn. This, of course, disrupts the support which must be carefully controlled during use. Knee supporting braces are often fitted by an orthotist who carefully shapes the brace to the patient's leg. In fact, the Castiglia brace is custom fitted to a plaster cast of the patient's leg. Thus, any deviation from the necessary positioning of the brace on the leg should be avoided.